The art of ink jet printing is relatively well developed. Commercial products such as computer printers, graphics plotters, and facsimile machines have been implemented with ink jet technology for producing printed media. The contributions of Hewlett-Packard Company to ink jet technology are described, for example, in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985); Vol. 39, No. 5 (October 1988); Vol. 43, No. 4 (August 1992); Vol. 43, No. 6(December 1992); and Vol. 45, No. 1 (February 1994).
Generally, an ink jet image is formed pursuant to precise placement on a print medium of ink drops emitted by an ink drop generating device known as an ink jet printhead. For example, an ink jet printhead is attached to a print cartridge body that is, for example, supported on a movable print carriage that traverses over the surface of the print medium. The ink jet printhead is controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to a pattern of pixels of the image being printed.
A typical Hewlett-Packard ink jet printhead includes an array of precisely formed nozzles in an orifice structure that is attached to or integral with an ink barrier structure that in turn is attached to a thin film substructure that implements ink firing heater resistors and apparatus for enabling the resistors. The ink barrier structure can define ink flow control structures, particle filtering structures, ink passageways or channels, and ink chambers. The ink chambers are disposed over associated ink firing resistors, and the nozzles in the orifice structure are aligned with associated ink chambers. Ink drop generator regions are formed by the ink chambers and portions of the thin film substructure and the orifice structure that are adjacent the ink chambers. To emit an ink drop, a selected heater resistor is energized with electric current. The heater resistor produces heat that heats ink liquid in the adjacent ink chamber. When the liquid in the chamber reaches vaporization, a rapidly expanding vapor front or drive bubble forces liquid within the ink chamber through an adjacent orifice.
A consideration with a printhead that employs heater resistors is reducing damage resulting from cavitation pressure of a collapsing drive bubble.